A novel GmFAD3-2a mutant allele developed through TILLING reduces alpha-linolenic acid content in soybean seed oil
2014
Hoshino, T. ((Saga University, Saga (Japan). Faculty of Agriculture, Laboratory of Plant Genetics and Breeding), (Yamagata University, Tsuruoka, Yamagata (Japan). Faculty of Agriculture, Laboratory of Plant Genetics and Breeding)) | Watanabe, S. | Takagi, Y. | Anai, T.
Soybean (Glycine max (L.) Merr.) oil typically contains 8% alpha-linolenic acid that is highly unstable and easily oxidized. This property is undesirable in many food and industrial applications. Genetic strategies for reducing alpha-linolenic acid content would enhance the commercial value. However, genetic resources for low alpha-linolenic acid content are limited among natural soybean variations. Microsomal omega-3-fatty acid desaturase (FAD3) is responsible for the synthesis of alpha-linolenic acid in the polyunsaturated fatty acid pathway. There are four FAD3 homologs (Glyma02g39230, Glyma11g27190, Glyma14g37350 and Glyma18g06950) in the soybean genome. While non-functional alleles have been reported for Glyma02g39230 (GmFAD3-1a) and Glyma14g37350 (GmFAD3-1b), little variation is seen in Glyma18g06950 (GmFAD3-2a). We isolated seven mutant GmFAD3-2a alleles, each containing a single-nucleotide substitution, from 39,100 independent mutant lines by using targeting induced local lesions in genomes (TILLING). Analysis of GmFAD3-2a transcripts and enzyme activities revealed that one missense mutant, 'P1-A9', contains a non-functional allele of GmFAD3-2a. By combining three non-functional alleles (GmFAD3-1a, GmFAD3-1b, and GmFAD3-2a), we generated soybean lines containing <2% alpha-linolenic acid in their seeds. The reverse-genetics-based development of novel mutant alleles in the fatty acid metabolic pathway will allow the improvement of soybean with better oil quality through conventional breeding.
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